Separating means for producing a thin-film solar module

ABSTRACT

Process and separating device for the production of a thin film solar module ( 10 ) comprising a plurality of solar cells ( 11 ) arranged side-by-side on a common substrate ( 12 ), which are produced by employing a plurality of layer deposition steps and layer separating steps during the course of cell production and which are electrically interconnected with one another, wherein after the application of a first contact layer ( 14 ) on substrate ( 12 ) and the cell-wise separation thereof a pn double layer ( 16 ) is applied on a contact layer and, thereafter, is mechanically separated in that a scraping cutting tool serving as separating device scrapes, by a relative movement to the coated substrate, a cell structure into said pn double layer, wherein said cutting tool slides, preferably without being raised or rotated, with a plane sliding surface of a flattened tip on said first contact layer ( 14 ) which has a higher hardness than said pn double layer ( 16 ).

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 09/521,694 now U.S. Pat. No. 6,319,747 Feb. 1, 2002 filed onMar. 9, 2000.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable

BACKGROUND OF THE INVENTION

The present invention relates to a process for producing a thin-filmsolar or photovoltaic module as well as to separating means for use inthis process.

One possibility for producing thin-film solar modules or thin-filmphotovoltaic modules comprising a plurality of solar or photovoltaiccells disposed in parallel on a common substrate, which are produced andelectrically interconnected by a plurality of cell-overlapping coatingsteps and coating-separation steps during cell production has alreadybeen described in U.S. Pat. No. 4,243,432. In that specification,CdS-Cu_(x)S solar cells are produced in that a glass substrate is alwayscompletely provided with deposited individual layers, one upon theother. The layers in form of thin films mainly comprise a hard contactlayer of SnO_(x) serving as the lower electrode and a pn double layer ofCdS-Cu_(x)S disposed on it as well as a further contact layer serving asthe upper electrode. Cuts performed between the individual thin filmdeposition steps have been provided to subdivide the cell-overlappingsubstrate film coating into individual cells, on the one hand, and toelectrically series-connect the cells of a substrate, on the other hand.For serial interconnection of the cells, the cuts are provided such thatthe upper electrode of a cell 1 contacts the lower electrode offollowing cell 2, however, is separated from the upper electrode of cell2. This scheme is continuously repeated over the whole substrate length.Various methods for separating the individual layers have been suggestedin this US patent, inter alia by ultrasonic techniques, and it has beenstated that the pn layer may also be separated for instance by means ofa rotating or a non-rotating cutting tool.

In U.S. Pat. No. 4,315,096, a similar process has been disclosed forCdTe and CdS layers wherein the separation cuts having a width ofbetween 5 μm and 100 μm are also produced either by mechanical methodsnot defined in detail or by means of laser beams. U.S. Pat. No.5,501,744, also, refers to the production of CdTe and CdS solar cells.According to U.S. Pat. No. 5,501,744, the modules are processed by meansof a tool head which is movable both in transversal and longitudinaldirection relative to the substrate. The tool head includes lasers,arranged side by side, sandblast blowers or deposition means which areobliquely directed to the substrate and, preferably, do not contact thesubstrate. After processing the substrate in longitudinal direction, thehead is displaced in transverse direction to a new starting position forlongitudinal movement. During the course of this transverse movement,the processing units are not activated.

As yet, however, commercially traded silicon solar cell modules havenot, as a rule, been fabricated in accordance with the above process ofU.S. Pat. No. 4,243,432. Rather, they have been made of individual cellswhich are interconnected by means of soldered-on metal strips. Modulescomprising CdS-Cu_(x)S solar cells have not so far been produced on anindustrial scale in accordance with the above-referenced process of U.S.Pat. No. 4,243,432. The same applies to CdS/CdTe solar cells which have,for a considerable time been considered as promising and which include afront contact of a transparent TCO layer, mostly in the shape of aso-called ITO layer. As to the production and the structure of such anindividual solar cell, explicit reference is made to European Patent No.EP 0,535,522, which corresponds to U.S. Pat. No. 5,304,499.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a process for producing a thin film solarmodule which is characterized in that a scraping tool as cutting orseparating means for the pn layer is used. Contrary to common cuttingmeans, the cutting tool employed in accordance with the presentinvention includes a flattened tip and the plane flattened surfaceserves as sliding surface of the tool. During the separating process,the tool is guided so that it slides with its plane sliding surface onthe first contact layer while the sliding surface rests with itscomplete flattened face on this layer which is in parallel to it. Thelongitudinal axis of the tool is in this case perpendicular to thecontact layer, or the substrate, respectively. By this design andarrangement, the danger of damage to the contact layer by the planesliding surface of the tool is reduced to a minimum. The adjustment ofthe pressing force exerted on the tool is substantially uncritical. Theforce may, without any danger, be adjusted at such a high value that thepn double layer is safely cut through. It is not necessary to providefor any sophisticated regulations and adjustments for the scribing orscraping depth of the tool. In addition, the tool may without anycomplicated adjustment be moved in any direction and may for instancefollow a meander-shaped path without any need of being axially rotatedbefore being forwarded to a new work area and before being moved in anew processing or cutting direction.

Contrary to the normally common technique of the application ofnon-rotating cutting tools such as raising and lowering tools, thecutting tool of the process according to the invention need not to beraised from the coated substrate, neither during the cutting process norwhen shifting the tool to a new work area. By avoiding a time consumingraising and lowering of the tool on and from the front contact layer,respectively, it was possible to increase the life time of the cuttingtool and to enhance the efficiency of the process.

It was an object of the present inventors to provide a process by whichan efficient production of thin film solar modules is possible whilemaking use of cell-overlapping thin film deposition and a rapid and safeseparating technique. A further object was to develop suitableseparating means for the production of thin film solar modules, whichmake such rapid and, at the same time, safe separation possible. Rapidseparation is necessary because the separation steps are part of thecontinuous production process and cannot be decoupled from it. Duringthe course of the separation process, in addition, it should be ensuredthat the desired layers are sufficiently completely cut through andseparated while the layers or thin films disposed under them remainundamaged.

The prior art scribing tools which are drawn, in an inclined positionand without a parallel sliding surface, over a substrate do not show theadvantages described above. U.S. Pat. No. 4,502,225 uses a scribing toolwhich is moved under an oblique angle of preferably 75° relative to thehorizontal (so-called back racking angle) over a substrate in order toseparate silicon layers. The tool preferably includes a rounded diamondtip. As alternatives for the obliquely disposed tool, pyramid-like ortruncated tips have been referred to. According to this US patent, thepressure adjustment of the tool and of its sharp scribing tip having apreferred diameter of about 0.01 mm is very critical. In order to obtaina defined scribing depth of the inclined tool rounded-off at the tipinto the layer to be cut while not damaging the underlying layer, thepressing force is adjusted to tight limits using a complicatedmechanical facility. One tries to monitor successful layer separation bymeans of resistance measurements, an action which can be ruled out inthe case of electrically not conducting layers. After cutting a layersegment over the whole substrate length, the tool is raised and shiftedinto the new scribing position where it is lowered again. The obliquescribing tool shown can be moved in one direction only.

U.S. Pat. No. 4,589,194 shows also a scribing stylus guided in aninclined position relative to the substrate surface which as analternative to the preferred diamond tip may optionally be producedcompletely of a hard metal. Amorphous silicon layers and back contactlayers disposed thereon are cut. In order to avoid that the TCO layerdisposed underneath be damaged by the sharp tool tip of only 0.006 mmdiameter maximum as well as by the relatively high pressing forces asrevealed, the Si layer is not completely cut but rather only so far thata certain thickness of the Si layer remains on the TCO layer. It is forthis reason that the stylus has to be adjusted very sensitively. Thestylus tip is ultrasonically driven. For shifting to a new scribingposition, the inclined stylus is raised from the substrate.

As compared to these scribing tools which have to be drawn in aninclined position over the coated substrates, the adjusting measures onthe scraping tool of the present invention with its sliding surfaceparallel to the substrate are considerably less complicated. Inaddition, the scraping tool may without being raised, be moved at a highspeed and in a precise and stable movement into various directions. Thetool according to the invention is guided perpendicularly over the thinfilm carrying substrate and slides with its sliding surfaceperpendicular relative to its longitudinal axis safely and gently on theharder contact layer and separate the overlaying layer reliably andcompletely.

The process of the invention is particularly suited for such CdS/CdTesolar cells as referred to having a front contact of a hard and smoothTCO layer such as the ITO layer which is about ten times harder than thesoft, brittle pn layer. Thereby, it is possible to cut the pn layerwhile not penetrating into the front contact material on which thecutting tool slides with its flattened tip when cutting the pn layer.The process is particularly efficient since the cutting tool need not beraised before moving it on to a new starting position. It is onlyshifted in a second transverse moving direction to reach a new startingposition before it is moved in a now-changed, generally opposite,longitudinal processing direction over the substrate. In this manner,the tool follows a meander-shaped path: It is moved in a firstlongitudinal direction over the whole module length, shifted in atransverse second moving direction in a marginal region of the moduleand moved in a longitudinal direction opposite to said firstlongitudinal direction. With a view to an efficient procedure, thispresent advantage cannot not be obtained by using cutting tools having arotating cutting head or cutting tools periodically raised from, andlowered to, the substrate. This also applies to the above-describedscribing tools that have to be guided in an inclined position.

Users who do not wish to shift the tools within a marginal area of themodules in said second transverse moving direction without raising thetool before it reaches a new starting position, may of course accept theprolongation of the process caused by the raising and lowering of thetool. When arranging a sufficient number of tools in parallelside-by-side in order to process the complete module in one workingstep, to raising and lowering during module coating does not applyanyway.

Since preferably the whole substrate is provided with the pn layer, thecutting tool when being shifted in said second moving direction cuts thepn layer and slides on the front contact layer within a marginal regionof the substrate. The process also covers a case in which the cuttingtool is shifted in the second moving direction in an edge area of thesubstrate, which is not provided with a pn layer on the front contactlayer.

When shifting on in the second transverse moving direction, it is notthe first cutting edge of the cutting tools which is used but rather adifferent tool side which is moved facing the second moving direction.After having been shifted to a new starting position, the cutting toolwhich is preferably provided with a rectangular sliding surface ismoved, preferably again without being raised and without being rotatedabout its longitudinal axis, opposite to the first moving direction.

It is of a constructional advantage to perform the relative movement inthe first moving direction during which the pn layer is cut by onlymoving the cutting tool, or the cutting tools, respectively, over thesubstrate.

Preferably, the cutting tool is resiliently pressed with its slidingsurface against the thin film carrying substrate. Sophisticatedadjustment measures of fixedly chucked cutting tools as required inconventional workpiece processing techniques are not necessary. By meansof the cutting tool of the invention resiliently pressed against thefront contact layer, the pn layer is always reliably cut.

By further optimizing the operation of the cutting tool, it was possibleto make the process still more efficient since at the beginning of thecutting tool operation, a tool is used the tip flattening of which has aconsiderable small value which in view of abrasion increases during theoperation period or tool life. In the process, the operation period islimited so that flattening and increase of the plane sliding surfaceremains within a tolerable range in which the tool still continues tocut sufficiently. As compared thereto, the initial tip flattening israther small at the beginning, however, already so large that the tooltip slides on the first contact layer without damaging it. In thisconnection, the pressure force of the tool depending on the adjustedspring force plays a role as well. Preferably, the pressure force isincreased with the abrasion-caused increase of the area of the flattenedtip in order to constantly produce a constant uniform optimum pressure.The force exerted by the spring is adjusted so that, on one hand, thefirst contact layer is not damaged and, on the other hand, sliding-up ofthe tool is avoided. In the production plant, the pressure force of thetools of the invention was adjusted only twice within a week while thetools were in uninterrupted operation.

The cutting means of the invention constitutes a cutting tool which issimple and economical to produce. Based on these properties, theexchangeable tool is suitable for the aimed-at mass production of thinfilm solar modules.

It has been found that particularly large separation distances of up to20 km could be obtained by using a rectangular sliding surface andpreferably unequally long cutting edges without having to exchange thetool and to interrupt the production process. Furthermore, it ispossible to work with a tip of the kind of an inverted four-sidedtruncated pyramid as tool tip by which, under equal cutting conditions,the first moving direction, or main scraping direction, is reversible.

It has also been found that by using the unequally long cutting edges,in the main scraping direction and in the moving or shifting directionpreferably rectangular thereto an optimum relation of the force to beapplied onto the cutting tool and the surface pressure can be obtained.The cutting tool according to the invention has the additional advantagethat even in case of a slightly oblique or angular run satisfactory cutsare made while, in addition to the cutting edge in the main scrapingdirection, the cutting edge in the moving or shifting direction comesinto operation. Thereby it is possible to provide for parallel cuts onthe substrate without the need of complicated readjustments of therelative angular orientations of substrate and tool.

Adjustment, mounting and movement of the tool perpendicular on thesubstrate can be obtained with little mechanical endeavors.

In the case of a CdS/CdTe pn double layer wherein the CdS layer has athickness in the range of only 100 nm or less, the thin CdS layeradheres so strongly to the first contact layer that it is not removed bythe cutting tool. Since, however, the CdS layer is so thin, itpractically shows the hardness of the hard first contact layerunderneath. For the flattened tool tip, therefore, identical slidingconditions are obtained. In case of thicker CdS layers, theirbrittleness becomes more and more evident so that they are removedtogether with the CdTe layer.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be explained in more detail basedon the drawings wherein

FIG. 1 is a diagrammatic top view of a thin film solar module having anedge zone freed from conductive material;

FIG. 2 is a cross sectional view through a portion of the module of FIG.1;

FIG. 3 is a lateral view of an example of a preferred embodiment of ascraping cutting tool according to the invention;

FIG. 4 is a lateral view of the cutting tool in the direction of thearrow of FIG. 3;

FIG. 5 is a view of the cutting tool tip enlarged relative to FIG. 3;

FIG. 6 is a view of the cutting tool tip enlarged relative to FIG. 4;

FIG. 7 again is a view of the cutting tool tip from the bottom enlargedrelative to FIG. 4;

FIG. 8 is a partial view of the cutting tool tip enlarged relative toFIG. 7;

FIG. 9 is a diagrammatic perspective view from the lower end of thecutting tool tip; and

FIG. 10 is a diagrammatic lateral view of a tool holder with a pluralityof cutting tools included in operational position above a modulesubstrate arranged on a table.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Thin film solar module 10 of FIG. 1 shows ten solar cells 11 on a glasssubstrate arranged in parallel side-by-side after the separation of thepn layer (preferably CdS/CdTe layer) before the application of the backcontact layer. A typical module includes about 100 individual cells permeter of its length. For the structuring of the module, therefore, aplurality of longitudinal cuts over large cutting lengths have to beperformed.

The sectional view of FIG. 2 shows substrate 12 with back contact 18applied. On glass substrate 12 consisting preferably of soda-lime glass,there is a TCO layer 14 which is cell-wisely separated and subdivided bycut 1. This cut which in the preferred embodiment is about 100 μm wideis generated through ablation by means of a laser, for instance aneodymium-YAG laser, after the application of the TCO layer. This firstcut defines the width of the cells to be series-connected.

After the application of pn double layer 16, preferably by CdSdeposition and subsequent CdTe deposition and activation of this layer,the cooled-off module is subjected to a cut 2 which constitutes a firstmechanical separation cut by means of the cutting tool of the invention.The cut separates pn layer 16 near first cut 1 up to TCO layer 14. Inthe beginning, the width of the cut in the present embodiment amounts toabout 0.06 mm which depends on the initial width of the tool and,especially, the flattened plane sliding surface thereof.

In a CdS/CdTe pn double layer wherein the CdS layer has a thickness inthe range of only 100 nm or less as compared to the CdTe layer which isabout 3 to 7 μm thick, the CdS layer is not removed as described above.The remaining CdS layer has only an insignificant influence on thefunction of the serial connection.

Subsequently, back contact 18 (preferably a double layer of asemiconductor layer, for instance tellurium, and a metal layer, forinstance nickel) is vapor-deposited. Subsequently, cut 3 is made, againby means of the cutting tool of the present invention whereby backcontact 18 and pn layer 16 are separated.

Cuts 1 through 3 extend in the longitudinal direction of strip-shaped,cells 11 as in accordance with the representation in FIG. 1. Suchlongitudinal cut performed, the tool is shifted, while preferably in thestill-coated substrate edge area, at right angles relative to thelongitudinal direction of cells 11 without being raised nor beingrotated about its longitudinal axis. Subsequently, the next longitudinalcut is made with the moving direction of the tool opposite to thepreceding longitudinal cut. The tool is therefore moved in a meander orsquare wave shape relative to the substrate. The tool of the presentinvention allows cutting speeds of 30 meters per minute. In manufacture,when operating a plurality of parallel cutting tools a speed of onlyabout 10 meters per minute is adjusted for the given modules.

During the course of the cutting or separating process, the cuttingscrap is removed by suction. Cleaning of the substrate prior to thefollowing coating step is not required.

As explained further above, series connection of the cells is obtainedby connecting the back contact of cell 1 to the front contact, i.e. TCOlayer 14 of cell 2, etc.

By using the inventional separation technique here described, the cellsmay, in principle, be interconnected in a different way as well.

Scraping cutting tool 30 shown in FIGS. 3 through 7 includes a tip 40having the shape of an inverted truncated cone. In accordance with thepreferred embodiment, the tool tip form is based on a four-sidedstraight pyramid having two differently long base edges 42 and 44 oflower base surface 41 of the truncated pyramid. These base edgesconstitute a first 42 and second 44 cutting edge of the tool. The sidefaces of the truncated pyramid extending from first and second cuttingor base edges 42, 44 have differently large aperture angles α and β.These side faces form the true rakes of the tool. The first, smaller,angle a defines true rake 46 in a first main scraping direction of tool30 and the second, larger, angle β defines the larger true rake 48 in asecond scraping direction for shifting tool 30. The first angle αdetermines the cutting or scraping width of the tool which during thecourse of the wear caused by abrasion increases to a tolerable value.

In the preferred embodiment, angle α=20° and angle β=70°. The shortercutting or base edge 42 of rectangular sliding surface 41 whichcorresponds to the base surface of the truncated pyramid has, in thepreferred embodiment, an original width of about 0.06 mm. The longerbase edge corresponding to the selected angle is initially 0.24 mm wide.In the preferred embodiment, the maximum cutting width given by themodule design amounts to about 0.1 mm. When operating tool 30, therespective true rake 46 forms in the preferred embodiment with thesubstrate plane, or the elongated sliding surface 41, an angle of γ=55°which becomes effective in the main scraping direction or the celllongitudinal direction. The larger true rake 48, on the other hand,forms with the substrate plane an angle of 80° which becomes effectivein cell cross direction, i.e. the transverse shift direction for thetool. In this direction, separating capacity and cutting width of thetool in the pn double layer of the preferred embodiment are of nosignificance since after the application of back contact 18 andcompletion of the module, the layers on the edge zone of the substrateare completely removed. By such removal of the layers, the structuresgenerated in the substrate layers by the movement of the tool in thetransverse moving or shift direction are eliminated.

The above-given values of the sliding surface may be varied by thoseversed in the art if layers have to be removed which e.g. to permitbroader separating strips. This applies for the angles as well. In thepresent preferred embodiment, however, the initial width of base edge 42is generally not less than 0.02 μm.

Truncated pyramid 40 passes over into a cylinder-shaped shaft 32 whichas demonstrated is provided on one side with a plane guiding face 34.

In the embodiment as shown, furthermore, tool 30 is provided on bothsides with a flattened tip 40 so that, when one tip is worn up, theother tip can be used. Because of the symmetric formation, thelongitudinal axis of the tool, or the longitudinal axis of the tool tip,respectively, is disposed perpendicular relative to sliding surface 41.

FIG. 10 shows a tool holder 50 wherein a plurality of tools areincorporated. For the production plant, twenty tools were arranged on alength of 20 cm. The tools simultaneously process a plurality of cellsarranged side-by-side on a substrate 10 which is fastened on a table 70.The table defines the X-Y plane for the relative movement ofsubstrate/workpiece. A spring 60 acts on each individual tool 30perpendicular to its sliding surface 41. Tools 30 are non-rotatablysecured in a spindle sleeve each by means of guiding face 34 of the toolholder. The spindle sleeve is moveable in longitudinal direction. Thetools are resiliently pressed against substrate 10.

The spring force is adjusted so that, on starting, the tool breaksthrough the layers to be separated from each other and during the courseof the separating movement constantly slides on contact layer 40. Asexplained further above, the spring force is preferably increased withthe increase of the sliding surface in order to maintain anapproximately even pressure. For the materials and geometries of thepreferred embodiment, a possible pressure range of some hundred N/mm² upto about 1000 N/m² was found. By lowering the tool holder in Zdirection, the springs, purchased from Federtechnik Knoerzer,Pfullingen, Germany, having various spring constants in the range from 1to 10 were subjected to varying forces. Thereby, the pressing force ofthe tool tip to the substrate was preferably adjusted so that thepressure amounted to 500 N/mm². During a one-week operational run oftools 30, the force exerted was readjusted for about four to eightNewton in order to compensate for surface abrasion and the surfaceincrease resulting therefrom.

In the preferred embodiment, tool holder 50 is moved, by means notshown, in the longitudinal direction of the cell. Between the processsteps performed in opposite directions, the table is transverselyshifted at right angles relative to the longitudinal direction of thecell corresponding to the number of the cells to be processed by thetools.

It should be noted that the tool of the invention may be operated aswell without the two moving directions described. A sufficient number oftools for all the cells of a substrate may, in principle, be arrangedside-by-side in a holder so that, by one single longitudinal cut,structuring of each layer can be obtained. Particularly in this case, itwould also be possible to use in the tool of the present invention a tiphaving the shape of a trilateral truncated pyramid. In principle, thetool tip of such an embodiment would need only one single cutting edgeso that the flattened tool tip could also be half round incross-section. In case of such geometrical embodiments of the tool tipit is also of advantage if the angle between the true rake(corresponding to surface 46 in FIG. 9) extending from the cutting edge(corresponding to edge 42) and the extension of flattened plane basesurface 41 of the tool tip (or the sliding cutting plane, respectively)is between 40° and 90° corresponding to angle γ in FIG. 5.

Instead of the truncated pyramid as explained, an inverted truncatedcone offers a further possible development of the tip of the toolaccording to the invention. Such shape is preferably used for theproduction of curved, for instance circular, cutting structures.

In the case of the truncated pyramid-shaped embodiment, the increase ofthe plane sliding surface width caused by abrasion decreases in the mainscraping or cutting direction with smaller values of α. Thereby, thelife time of the tool can be increased. The stability of the tool,however, is decreased, which by increasing β can be increased to acertain extent only. In the case of a preferred range of α of between15° and 40°, values for β in the range of from 100° to 50° have provedto be suitable, which in the case of a given cutting edge ratio and ageometrically exact truncated pyramid can be calculated from the valuesof α. Depending on the material be separated and the hardness of thefront contact layer, those skilled in the art will, with a view tohighest possible cutting speed and life time of the tool, find values.which for their demands constitute the best possible compromise.

In this connection, those skilled in the art need not, as in thepreferred embodiment, presume a geometrically exact straight four-sidedtruncated pyramid but may also combine such aperture angles wherein theextensions of the true rakes do not meet at a common tip. However,easier reproducible production of the tool is possible in case of ageometrically exact truncated pyramid. Furthermore, due to the constantcutting edge ratios in this case, it is also easier to calculate thesurface increase caused by abrasion and the pressing force adaptation.

The sliding surface which is not equilaterally rectangular in thepreferred embodiment can also be replaced by a square one. This will beof advantage if not only longitudinal cuts but also lateral cuts of evenwidth have to be produced in a pn layer.

In the preferred embodiment, the cutting tool according to the inventionconsists of Widia steel (Type THM-U by Widia, Essen, Germany). Inaddition to other hard metals, a flattened diamond tool tip with a planesliding surface would in principle also be suited.

What is claimed is:
 1. Separating means for mechanically separating a pndouble layer of a thin film solar module including a plurality of solarcells arranged side-by-side on a common substrate, which are produced byemploying a plurality of layer deposition steps and layer separationsteps during cell production and which are electrically interconnectedwith one another, said pn double layer being provided on a first contactlayer which has a higher hardness than said pn double layer, whereinsaid separating means has at least one scraping cutting tool (30) forcutting by scraping into said pn double layer of the plurality of solarcells, each tool having a flattened tip (40) with a plane slidingsurface (41) arranged so that the entire plane sliding surface rests onsaid first contact layer during scraping.
 2. Separating means accordingto claim 1, wherein said at least one scraping cutting tool (30) has theshape of an inverted truncated pyramid, the smaller base surface ofwhich forms said plane sliding surface (41).
 3. Separating meansaccording to claim 2, wherein the pyramid from which the truncatedpyramid is formed is a four-sided straight pyramid, wherein the planesliding surface has first and second cutting edges for first and secondmoving directions of the at least one cutting tool, respectively, andwherein lateral faces of said truncated pyramid extend from said firstand second cutting edges (42, 44), which lateral faces constitute truerake surfaces (46, 48) of said at least one cutting tool (30), andwherein the lateral face extending from the first cutting edge extendsat an angle with respect to a central axis of the pyramid that issmaller than the angle formed by the lateral face extending from thesecond cutting edge with respect to the central axis of the pyramid. 4.Separating means according to claim 1, wherein the sliding surface (41)of said at least one scraping cutting tool has a first and a secondcutting edge (42, 44) for cutting in a first and a second movingdirection of said at least one scraping cutting tool (30), respectively.5. Separating means according to claim 4, wherein said sliding surface(41) is rectangular and wherein the first cutting edge (42) for thefirst moving direction is shorter than the second cutting edge (44) forthe second moving direction.
 6. Separating means according to claim 1,wherein said sliding surface (41) is rectangular.
 7. Separating meansaccording to claim 1, wherein said at least one scraping cutting tool(30) is made of metal.
 8. Separating means according to claim 7, whereinthe metal is steel.
 9. Separating means according to claim 1, whereinsaid at least one scraping cutting tool (30) is adapted to be movedrelative to said substrate in sliding contact therewith such that saidflattened tip (40) slides on said first contact layer and wherein saidat least one cutting tool (30) is adapted to be guided by means of atool holding and guiding means(50) so that the plane sliding surface(41) provided by the flattened tool tip rests with its full planesurface on said first contact layer (14) and is guided parallel to saidsliding surface.
 10. Separating means according to claim 1, wherein saidat least one scraping cutting tool (30) is adapted to be moved withoutbeing rotated and without being raised, in different directions relativeto said layer-carrying substrate (12) to reach new starting positionsand to perform separations in different directions.
 11. Separating meansaccording to claim 1, wherein said at least one scraping cutting tool(30) is adapted to separate a second contact layer on said pn doublelayers which contact layer is applied after having separated said pndouble layer by means of the at least one scraping cutting tool, andwherein said at least one scraping cutting tool is adapted to be guidedby means of a tool holding and guiding means (50) so that said secondcontact layer is separated together with said pn double layer disposedtherebeneath by means of said at least one scraping cutting tool (30)along predetermined cutting lines, said flattened tool tip (40) slidingagain on said first contact layer.
 12. Separating means according toclaim 1, wherein a plurality of scraping cutting tools (30) are providedin tool holding and guiding means (50) for being guided in common in afirst moving direction for cutting and for being subsequently shifted incommon on to a next not-yet separated cell group in a second movingdirection for shifting.
 13. Separating means according to claim 1,wherein said separating means comprises means (60) for resilientlypressing said at least one scraping cutting tool (30) with its flattenedtip (40) against said layer carrying substrate surface.
 14. Separatingmeans according to claim 1, wherein said at least one scraping cuttingtool (30) is adapted so that a cutting edge (42) of the tool initiallyhas a minimum permissible length which is increased to a maximumpermissible length reached at the end of the at least one tool'slifetime due to the increase of the length due to abrasion of the atleast one tool.
 15. Separating means according to claim 1, wherein saidthin film solar module has a CdS/CdTe pn double layer with a CdS layer,and wherein the CdS layer is deposited on said first contact layer,wherein the CdS layer has a thickness within the range of 100 nm orless, and wherein the at least one scraping cutting tool (30) is adaptedso that said flattened tip (40) of the at least one cutting tool (30)slides on the CdS layer.